Wireless network has many advantageous features and is therefore capable of eliminating many drawbacks of wire network. Recently, wireless meshing networks based on IEEE 802.11 wireless network protocol have become the trend of current wireless network development. Such trend is significant in view of how to develop wireless meshing networks based on interconnection of access points (APs). However, no standard for IEEE 802.11 wireless networking based meshing networks has been published by IEEE because IEEE did not anticipate that IEEE 802.11 will develop so quickly at the time of publishing IEEE 802.11. Further, no relevant draft has been initiated yet. Thus, many network service providers have begun to develop their own wireless meshing networks.
There are many significant differences in terms of physical features between a wire network and a wireless network. Services provided by a wireless network are also different from that provided by a wire network. Further, a number of potential problems exist when a wireless network and a wire network integrate. Most of wireless meshing networks developed by the network service providers cannot satisfy needs of vast users. The wireless meshing networks are not flexible as compared with wire meshing networks. Moreover, many problems about network establishment, meshing establishment and maintenance, and network management are yet solved. Such problems also exist and are yet solved in developing wireless meshing networks in a wireless distribution system (WDS).
In addition, performance of a wireless network is closely related to a wireless meshing. This is because wireless medium is shared and is a limited resource. It highly depends on the implementation of Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA). Thus, it is important to effectively share wireless bandwidth among computers. Further, interference and noise may adversely affect the transmission performance of a wireless link. It is understood that the transmission performance of a wireless network may decrease to about half when a new wireless link is established in the wireless network according to many available documents. Further, a wireless network may degrade due to wireless meshing network growth. As a result, the performance of a wireless network is low while it is busy all the time.
Referring to FIGS. 1 and 2, two prior wireless meshing networks are shown. Either wireless meshing network has an AP connected to a wire network. The connected AP has its signals covered the remaining three APs disconnected from the wire network. Four APs in FIG. 1 are located about the same as that in FIG. 2, except that AP 1-4 is in direct wireless connection to AP 1-1 in FIG. 1 and AP 2-4 is not in direct wireless connection to AP 2-1 in FIG. 2. There are three APS including AP 1-2, AP 1-3, and AP 1-4 not in direct wireless connection to the wire network as shown in meshing in FIG. 1. For transmitting data over the wire network, for example, AP 1-4 wants to send a packet to AP 1-1 and thus AP 1-4 may first send a Request To Send signal (RTS) to AP 1-1. After receiving the RTS, AP 1-1 may send a Clear To Send signal (CTS) to other adjacent APs to wait if AP 1-1 is ready to receive the packet. This can avoid collision when AP 1-4 sends a packet. In other words, other APs in the meshing in FIG. 1 will wait (i.e., stop sending packet) when AP 1-4 sends a packet.
The above case is also applicable to meshing in FIG. 2. It is seen that wireless meshing in FIG. 2 is different from that shown in FIG. 1. Thus, in a case of AP 2-4 sending packet to AP 2-1, AP 2-4 must first send RTS to AP 2-3. After receiving the RTS, AP 2-3 may send a CTS to other adjacent APs to wait if AP 2-3 is ready to receive the packet. This can avoid collision when AP 2-3 sends a packet. In detail, no collision occurs when AP 2-4 sends a packet to AP 2-3 if AP 2-2 is covered by AP 2-3 in signal transmission. As compared with meshing in FIG. 1, AP 2-3 has to perform the same transmission again in order to send the packet transmitted from AP 2-4 to AP 2-1. In comparison, AP 1-4 has a transmission performance higher than that of AP 2-4.
Similarly, as shown in meshing in FIG. 2 in a case of AP 2-4 sending a packet to AP 2-1 AP 2-2 sends a RTS to AP 2-1 if AP 2-2 is not covered by AP 2-3 in signal transmission and AP 2-2 also wants to send a packet to AP 2-1. At this time, AP 2-2 will send a RTS to AP 2-1 if AP 2-1 wants to receive the packet transmitted from AP 2-2. But AP 2-1 may be interfered by AP 2-3 when AP 2-2 sends a packet to AP 2-1. As a result, the transmission performance is low. Likewise, AP 2-3 may be interfered by AP 2-1 when AP 2-1 sends an acknowledge signal (ACK) to AP 2-2. Thus, in view of wireless meshing networks in both FIG. 1 and FIG. 2, more wireless links in the packet transmission path may not only decrease the transmission performance but also cause interference. Thus, smaller hop count regarding connecting to a wire network can increase the transmission performance of a wireless meshing network.
Referring to FIG. 3, a stable wireless meshing network is shown. AP in the network is labeled by AP a-b where “a” represents the number of hop(s) that an AP passes prior to connecting to a wire network and “b” represents the b-th AP passed hop(s) prior to connecting to the wire network. Referring to FIG. 4, a new AP X-Y is added in the wireless meshing network in FIG. 3. AP X-Y is in partial signal coverage with AP 2-2, AP 3-3, and AP 4-4. The added AP X-Y is connected to AP 3-3 or AP 4-4 and the meshing is expanded. Thus, the added AP X-Y is labeled as AP 4-5 based on the above naming rule. The number of APs that AP 2-1 is about to service is larger than the number of APs that AP 2-2 is about to service. Thus, a packet may follow a path from AP 4-5, AP 3-3, and AP 2-1 to AP 1-1 prior to sending to a wireless meshing network. However, the transmission performance is low because bandwidth is narrow due to contention. To the contrary, the transmission performance can be increased if bandwidth is made wide due to less contention by causing the added AP X-Y to be in direct wireless connection to AP 3-4. For the same reason, the transmission performance can be further increased by decreasing the number of hop(s) that an AP passes prior to connecting to a wire network by causing the added AP X-Y to be in direct wireless connection to AP 2-2. To the contrary, the transmission performance of a wireless network may decrease to about half when hop count increases by one in the packet transmission path.
In view of above, it is thus desirable among wireless network service providers to achieve the following goals. In a case of adding an AP to a wireless meshing network how to enable the AP to select a less complicated wireless meshing network based on received signals when the wireless meshing network is expanding. Alternatively, how to decrease the number of hop(s) that an AP passes prior to connecting to a wire network in order to decrease hop count of the meshing and decrease the number of times of repeatedly sending the same packet in a wireless environment and thereby increase the transmission performance of the wireless network, decrease network load, prevent interference from occurring, optimize wireless link, effectively increase bandwidth utilization, and solve the problem of load unbalance.